Think of how "infected" Lahabrea acted due to Athena. It was a lot like the Lahabrea we know, right? I don't think Pandaemonium survived the Sundering, but I DO think that infected Lahabrea had done something with it to throw it in the Lifestream. Why there? Because Athena is in the Lifestream, and throwing Pandaemonium there gives Athena access to it and her research again. With Claudien likely being Eric's reincarnation, and it being told to us that Athena needed his soul for some reason, all the pieces have gathered into one area. We didn't change the past at all, we just moved all the pieces on the board in place inadvertently...for Athena. she has played the long game, and now she has everything she needs to complete her evil plans, at least until we stop her.